[PATCH] D70284: Constant strings emitted when `-fno-constant-cfstrings` is passed should allow dead stripping

[Ben D. Jones via Phabricator via cfe-commits]

bendjones updated this revision to Diff 229441.
bendjones added a comment.

Added `"objc_arc_inert"` and updated `clang/test/CodeGenObjC/ns-constant-strings.m` tests to make sure the section is emitted as we want.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D70284/new/

https://reviews.llvm.org/D70284

Files:
  clang/lib/CodeGen/CGObjCMac.cpp
  clang/test/CodeGenObjC/ns-constant-strings.m


Index: clang/test/CodeGenObjC/ns-constant-strings.m
===================================================================
--- clang/test/CodeGenObjC/ns-constant-strings.m
+++ clang/test/CodeGenObjC/ns-constant-strings.m
@@ -33,7 +33,14 @@
 // CHECK-NONFRAGILE: @"OBJC_CLASS_$_NSConstantString" = external global
 
 // CHECK-FRAGILE: @.str = private unnamed_addr constant [6 x i8] c"MyApp\00"
+// CHECK-FRAGILE: @_unnamed_nsstring_ = private constant %struct.__builtin_NSString { i32* getelementptr inbounds ([0 x i32], [0 x i32]* @_NSConstantStringClassReference, i32 0, i32 0), i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str, i32 0, i32 0), i32 5 }, section "__OBJC,__cstring_object,regular"
 // CHECK-FRAGILE: @.str.1 = private unnamed_addr constant [7 x i8] c"MyApp1\00"
+// CHECK-FRAGILE: @_unnamed_nsstring_.2 = private constant %struct.__builtin_NSString { i32* getelementptr inbounds ([0 x i32], [0 x i32]* @_NSConstantStringClassReference, i32 0, i32 0), i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str.1, i32 0, i32 0), i32 6 }, section "__OBJC,__cstring_object,regular"
 
 // CHECK-NONFRAGILE: @.str = private unnamed_addr constant [6 x i8] c"MyApp\00"
+// CHECK-NONFRAGILE: @_unnamed_nsstring_ = private constant %struct.__builtin_NSString { i32* bitcast (%struct._class_t* @"OBJC_CLASS_$_NSConstantString" to i32*), i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.str, i32 0, i32 0), i32 5 }, section "__DATA,__objc_stringobj,regular"
 // CHECK-NONFRAGILE: @.str.1 = private unnamed_addr constant [7 x i8] c"MyApp1\00"
+// CHECK-NONFRAGILE: @_unnamed_nsstring_.2 = private constant %struct.__builtin_NSString { i32* bitcast (%struct._class_t* @"OBJC_CLASS_$_NSConstantString" to i32*), i8* getelementptr inbounds ([7 x i8], [7 x i8]* @.str.1, i32 0, i32 0), i32 6 }, section "__DATA,__objc_stringobj,regular"
+
+// CHECK-FRAGILE: attributes #0 = { "objc_arc_inert" }
+// CHECK-NONFRAGILE: attributes #0 = { "objc_arc_inert" }
\ No newline at end of file
Index: clang/lib/CodeGen/CGObjCMac.cpp
===================================================================
--- clang/lib/CodeGen/CGObjCMac.cpp
+++ clang/lib/CodeGen/CGObjCMac.cpp
@@ -1978,6 +1978,7 @@
   return V;
 }
 
+// This is only used when `-fno-constant-cfstrings` is given
 ConstantAddress
 CGObjCCommonMac::GenerateConstantNSString(const StringLiteral *Literal) {
   unsigned StringLength = 0;
@@ -2029,13 +2030,12 @@
   GV = Fields.finishAndCreateGlobal("_unnamed_nsstring_", Alignment,
                                     /*constant*/ true,
                                     llvm::GlobalVariable::PrivateLinkage);
-  const char *NSStringSection = "__OBJC,__cstring_object,regular,no_dead_strip";
-  const char *NSStringNonFragileABISection =
-      "__DATA,__objc_stringobj,regular,no_dead_strip";
-  // FIXME. Fix section.
+  const char *NSStringSection = "__OBJC,__cstring_object,regular";
+  const char *NSStringNonFragileABISection = "__DATA,__objc_stringobj,regular";
   GV->setSection(CGM.getLangOpts().ObjCRuntime.isNonFragile()
                      ? NSStringNonFragileABISection
                      : NSStringSection);
+  GV->addAttribute("objc_arc_inert");
   Entry.second = GV;
 
   return ConstantAddress(GV, Alignment);


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